# EPUBCheck HTM_055: discouraged HTML element, how to fix it

Source: https://epubcc.com/epubcheck/htm_055/ (updated 2026-11-04)

EPUBCheck HTM_055 is a usage message: “The "…" element should not be used (discouraged construct).” The document uses an HTML element that EPUB discourages. EPUB 3.3 lists base, rp and embed as discouraged constructs because they cause interoperability problems; EPUBCheck names the element and reports it as a usage note.

- Official message (EPUBCheck 5.4.0): The "%1$s" element should not be used (discouraged construct)
- Default severity: Usage

## Typical causes

- A base element copied from a web page, which can make relative links point to a website.
- rp elements around ruby annotations, which EPUB 3 reading apps do not need.
- An embed element used for scripted or interactive content.

## How to fix it

1. Open the file EPUBCheck names (the message gives the path, line and column) in a text or EPUB editor such as Sigil, or unzip the EPUB and open it there.
2. Remove base elements and make sure every link is relative to the chapter itself.
3. Remove rp elements and keep the ruby and rt markup.
4. Replace embed with object, which has a fallback mechanism, or with a plain image.
5. Rebuild the EPUB and run EPUBCheck again to confirm the message is gone.

## When it's not this

If the element is outdated rather than discouraged, EPUBCheck reports it as OBS-001.

## Sources

- EPUB 3.3, §6.1.4.3 Discouraged constructs: https://www.w3.org/TR/epub-33/#sec-xhtml-deviations-discouraged (read 2026-11-04)

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EpubCC.